Are CRUD webapps today the modern version of the "expert system"?
The key feature of an expert system is that the knowledge base is structured to be traversed by the inference engine.  Web sites like Stack Exchange don't really use an inference engine; they do full-text searches on minimally-structured data.  A real inference engine would be able to answer novel queries by putting together answers to existing questions; Stack Exchange sites can't even tell if a question is duplicate without human confirmation.